User guide

March 2005 Understanding Canopy Networks
Through Software Release 6.1
Page 74 of 425 Issue 1
Canopy System User Guide
In all other Canopy frequency band ranges, round-trip latency is typically
◦ 20 msec with software scheduling.
◦ 6 msec with hardware scheduling.
At range settings of greater than 40 miles (64 km) in the 900-MHz AP, more time elapses
between transmit and receive cycles to compensate for greater air delay. In each frame,
this reduces the number of data slots, which slightly reduces the aggregate throughput of
the link. However, the throughput is as predictable as in other Canopy point-to-multipoint
links.
Throughput is a factor of the Max Range parameter in the AP and is effective for all SMs,
regardless of their distance from the AP. The aggregate useful throughput for each AP in
the other Canopy frequency band ranges is 6.2 Mbps with software scheduling (7 Mbps
with hardware scheduling), regardless of the downlink percentage setting. This
throughput includes all downlink data to all SMs and all uplink data from all SMs that link
to the AP.
The downlink throughput to a single SM can be greater than 4 Mbps. The uplink
throughput to an AP can be as great as approximately 2 Mbps, depending on the
uplink/downlink ratio. However, setting the ratio to 50% for a point-to-mulitpoint Canopy
link does not yield an even division of bandwidth between uplink and downlink traffic. This
is evident in the throughput values that are quoted in Table 17 and Table 18.
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NOTE:
These values were derived from the Link Test web pages of Canopy
modules. For the link tests, the Total NumUAckSlots, NumDAckSlots,
and NumCtlSlots parameters were set to the default value of 3.
Table 17: Downlink and uplink PTMP throughput, 2-mile link, software scheduling
Downlink
Percent
Data Slots
Down
Data Slots
Up
Downlink
Throughput
(MHz)
Uplink
Throughput
(MHz)
95 31 2 4.9 0.4
90 30 3 5.1 0.5
85 28 5 5.6 0.8
80 26 7 4.9 1.1
75 25 8 4.9 1.2
70 23 9 4.4 1.3
65 21 11 3.9 1.5
60 20 12 3.9 1.6
55 18 14 3.6 1.7
50 16 16 3.3 1.9
45 15 17 3.0 2.0